1. Field of the Invention
The present invention provides a wireless communication receiving system and an apparatus and a method for deciding a transmitted signal corresponding to a received signal thereof. More particularly, the present invention provides a Multi-Input Multi-Output (MIMO) wireless communication system, an apparatus, and a method for deciding a transmitted signal corresponding to a received signal thereof.
2. Descriptions of the Related Art
With increased demands for personal communications and the rapid proliferation of multimedia message communications over recent years, the frequency spectrum has become an increasingly valuable resource. Accordingly, improving the communication throughput has become one of the greatest challenges confronted by the wireless communication industry. One of the effective solutions that have been proposed to solve this problem is the Multi-Input Multi-Output (MIMO) technology.
In a MIMO wireless communication system, the transmitting end divides an original transmitted signal into a plurality of sub-transmitted signals according to the number of antennas and transmits the sub-transmitted signals from the transmitting antennas to the receiving antennas at a receiving end through channels. These sub-transmitted signals are then combined again into a received signal by the receiving antennas according to a channel propagation factor. Because the transmitted signal is subject to interference from noise during transmission, differences may exist between the received signal and the transmitted signal. Consequently, how to decide a transmitted signal corresponding to a received signal has become a great concern that many research efforts are directed to in this industry.
One conventional method for deciding a transmitted signal corresponding to a received signal is to make a computation according to the Maximum Likelihood algorithm. In this method, each of the possible candidate transmitted signals is used respectively in the computation, and the one that is computed to be most approximate to the received signal is chosen as the transmitted signal corresponding to the received signal. Although this method may yield a relatively accurate result, it requires a computation on every candidate signal. In the case of a high level quadrature amplitude modulation (QAM), the computational complexity of this method will be undesirably high. For example, in an N by N MIMO wireless communication receiving system, if the QAM has a level of M, the computational complexity will be as high as O(MN).
Another conventional method for deciding a transmitted signal corresponding to a received signal is to make a computation according to the Sphere Decoding algorithm. In this method, a sphere radius is decided first, and among the candidate transmitted signals within this sphere radius, the one that is computed to be most approximate to received signal is chosen as the transmitted signal corresponding to the received signal. Although this method may reduce the number of candidate signals to be computed, it may be difficult to decide the appropriate sphere radius. Moreover, the corresponding hardware is also difficult to implement.
Accordingly, it is important to provide a method, which has reduced computational complexity and allows for easy hardware implementation, for deciding a transmitted signal corresponding to a received signal in a wireless communication receiving system.